The present invention relates generally to the field of floor systems in which a support base is covered by a plurality of floor panels secured to the support base with an adhesive. More particularly, the present invention relates to a floor system which includes a plurality of spaced pre-cured elongated elastomeric support members positioned between the floor panels and the support base for cooperation with an adhesive with vertical grade trowelable viscosity to provide uniform resilient cushioning and uniform elastic energy return for the floor system, to provide a bridging action over depressed spots in an uneven support base, and to provide restraint against unwanted lateral movement or vertical buckling.
Resiliently cushioned floor systems are in common use in gymnasiums and other indoor sporting activity areas, as well as in high-rise residential condominiums and other types of buildings where impact-cushioned comfort underfoot and impact-sound reduction between floors are important design considerations. In such floor systems, a flat upper surface is provided by arranging a plurality of floor panels in a side-by-side abutting relationship to provide a flat surface with essentially no openings between floor panels.
Such resiliently cushioned floor systems should provide for minimum maintenance and, in normal use, should withstand unwanted lateral expansion, buckling, dead spots, warpage, and other forms of surface deficiencies and irregularities. For indoor sporting areas, a floor should be resiliently cushioned to help prevent leg injuries, such as shin splints, and should have good elastic energy return to help reduce fatigue from vigorous exercising. The floor surface should also absorb impact-generated sound between floors of multi-story buildings.
U. S. Pat. No. 4,233,793, issued to Ray E. Omholt, inventor of the floor system described in the present application, shows and describes a resiliently cushioned wood flooring system and a method for installing such a system and is hereby incorporated by reference. In the system described in the Omholt patent, wooden flooring members or floor boards are secured to a support base utilizing an uncured elastomeric adhesive which is spread on either the support base or on the floor boards or on both in spaced ridges with a relatively uniform thickness. Typically, the adhesive is applied to the support base. Spherical beads of a uniform diameter and made of a material such as cured elastomeric urethane, styrene, or some other material which will easily deform under subsequent walking loads once the floor is in use are installed between and within the adhesive ridges. The diameter of the beads is selected to be less than the thickness of the uncured adhesive ridges being applied. The beads have the initial support capability needed to maintain the floor boards at the desired distance above the support base during installation under the relatively light hand-loading applied by flooring installers as the flooring is forced down into the relatively soft vertical-grade elastomeric adhesive while the floor boards are being laid. The beads do not, and are not intended to, provide resistance to deformation under the force of walking and other loads which are applied to the floor in normal use. Once the elastomeric adhesive is cured, the adhesive cooperates with the gaps or spaces between the adhesive ridges to provide resilient cushioning and support for the flooring system, and the initial vertical spacing function provided by the spherical beads is no longer of consequence.
Although the wood flooring system and the method of installation shown and described in the aforementioned patent have gained widespread acceptance, the flooring system suffers from certain drawbacks which limit its use under some circumstances. One such drawback is that it is difficult to be sure that the flooring installers laying the floor are using the proper number of beads and that the flooring installers are positioning the beads properly to initially support the floor boards at the desired height from the support base during the curing of the elastomeric adhesive. The careful positioning of the beads in the elastomeric adhesive as it is being spread and before the flooring is laid is very time consuming, and some floor installers may have a tendency to reduce the number of beads under the flooring or a tendency to eliminate the beads entirely in order to save time and effort, thus adversely affecting the cushioning and the impact-sound absorbing qualities of the floor.
Another drawback of the prior flooring system is that even if the proper number of beads are utilized, and even if the beads are uniformly distributed over the support base, the beads do not provide enough support to permit the floor to be walked on until after the elastomeric adhesive has cured for a period of time which is normally not less than twenty-four hours. In the installation of cushioned flooring in commercial buildings, such as high-rise buildings, workers of non-flooring trades frequently cannot be kept off a freshly-laid floor for the time required for the elastomeric adhesive to properly cure, due to the demands of their own work schedules. Thus, it is not uncommon that someone on a commercial job might walk on a newly-laid floor causing severe damage such as adhesive squeeze-through between the floor boards and poor cushioning and poor sound attenuation between floors in the areas where the floor was walked on prior to curing. It would also be necessary to repair or replace the damaged floor boards, a costly and time consuming job.
Another drawback of the prior flooring system is that localized depressions in a concrete support base known as "bird baths" can cause substantial problems if the floor boards being applied have a length which spans the depression. Since the elastomeric adhesive is applied in a uniform thickness, the adhesive would not contact the backs of the floor boards spanning the depression if the depression being spanned by the boards were deeper than the thickness of the adhesive being applied. The spherical beads positioned in the adhesive might be the only material in contact with the bottoms of the floor boards in question. The spherical beads are inadequate for supporting the floor boards after the adhesive has cured and walking loads are applied to the floor since the spherical beads will become crushed resulting in the floor being unsupported in the area spanning the depression.
Another drawback of the prior flooring system is that the amount of elastomeric adhesive required to provide resilient cushioning is substantial, and the work of applying it is messy. This effectively prohibits the installation of pre-finished flooring using this method, and pre-finished flooring is the flooring of choice in high-rise construction because of the ever present dirt which makes on-the-job finishing of the floors in a satisfactory manner almost impossible.
The present invention overcomes the foregoing drawbacks and deficiencies of the flooring system of the prior patent by providing a plurality of pre-cured elongated elastomeric cushioning support members which fully support the floor panels under initial and in-use loads. The pre-cured elastomeric support members positioned between the support base and the floor panels are designed to be able to support normal walking loads, even if the floor is freshly-laid, so that substantially no support is required from the uncured elastomeric adhesive. Utilizing elongated elastomeric support members which are preferably in the form of a generally continuous open grid, there is no problem with lack of initial support over the entire surface area to be covered by the floor panels. The present invention also reduces substantially the potential problem of adhesive squeezing up between floor boards, a problem which might normally be anticipated if a newly-laid floor was walked on prior to curing of the elastomeric adhesive.
It is common in the flooring industry for floor panels to have a substantial length and a rather narrow width. Such panels are able to easily span "bird bath" depressions in concrete support bases during installation. An example of such flooring might be oak-surfaced plywood planks measuring about six feet in length and about four inches in width. Another example might be plywood sheets intended for use as a subfloor and measuring eight feet by four feet. It should be noted that it is quite common in the flooring industry for the support base in gymnasiums or in high-rise condominiums to be constructed of concrete, and for the surface of the concrete to be somewhat irregular. Heretofore, such unevenness in the support base has resulted in hollow sounding spots, inadequate support, and dead spots under impact on the floor where the floor panels are bridging depressed locations in the support base. With the current invention, the pre-cured elongated elastomeric support members and the elastomeric adhesive ridges cooperate to overcome the problem caused by minor surface depressions without the sacrificing of support for the floor over such depressions once the adhesive has cured since the effective support distance between the support base and the floor is the combined thickness of the support members and the thickness of the applied adhesive.
With the flooring system of the above-identified Omholt patent, bridging could result in the bottoms of the floor panels being lifted above contact with the applied adhesive over low spots in the support base, leaving the floor panels supported only by contact with the crushable spherical beads. With the present invention, pre-cured elongated elastomeric support members which can fully support the floor panel under normal in-use loads can be attached to the under-side of the floor panels at the point of manufacture. Where such floor panels span unevenness in the support base, great flexibility of support can be obtained. Where a localized portion of the support base is high, the elongated support members penetrate the soft uncured elastomeric adhesive as required. Where a localized portion of the support base is low, it is only necessary for the bottoms of the elastomeric support members to be in contact with the elastomeric adhesive ridges for firm support to occur after the elastomeric adhesive has cured. This is a vital quality control to assure control of dead spots while preserving the desired minimum degree of cushioning and impact-sound attenuation in the case of multi-story residential buildings.
Most support bases located on-grade (resting directly on earth) are formed with concrete slabs. Water vapor from damp earth underneath frequently penetrates such slabs and causes unwanted expansion and warpage to wood-based materials laid over such on-grade slabs. By using a moisture-curing elastomeric adhesive to secure the floor panels to the support base, the water vapor problem is very frequently overcome because of the inherent ability of the adhesive material to control the penetration of water vapor coming through on-grade concrete slabs. One preferred such adhesive material, Tremco V-60, is produced by Tremco, Inc., in Cleveland, Ohio, and is a one-component vertical-grade urethane elastomer with a perm rating of 0.02 metric perm-centimeters when tested in accordance with ASTM E96-66, Procedure E. Another effective method for dealing with dampness coming from damp support bases is to position a generally continuous moisture-resistant membrane layer between the undersurface of the floor panels and the upper surface of the elastomeric support members.
By applying the elongated elastomeric support members to the bottom side of the floor panels at the point of manufacture, all questions of potential improper spacing of the support members or of a less-than-designed cushioning height beneath the floor panels or of improper impact-sound reduction under the floor panels caused by installer error or minor variations in the planarity of the support base are eliminated. The end result is a floor system with a much higher degree of predictable cushioning and impact-sound absorbency, a floor system with a substantially greater tolerance for the unevenness which can be anticipated in many concrete support bases, a floor system which makes possible a substantially faster application of the floor panels, and a much neater job with less likelihood that any of the floor panels might have to be replaced due to installer error, uneven concrete, or due to the carelessness of workers from other trades. Also, with a very wide selection of pre-cured elastomeric support members from which to choose, degrees of cushioning and elastic rebound energy become much more predictable, and the neatness of installation makes possible the use of pre-finished flooring.